Define angle of contact. for what nature of angle of contact will a liquid wet the solid
Answers
Answered by
8
The process of wetting of a solid surface is better explained with cohesive and adhesive forces. Wetting of a solid surface by a liquid means the liquid molecules succeeded in maintaining a contact with the surface through the inter molecular attractive forces. You should see that every liquid may not stick on to a given surface and similarly every surface may not get by a given liquid.
A liquid has it's own inter molecular force of attraction that maintains it's continuity. Such forces existing between same type of molecules is called cohesive force. Now if there is some inter molecular attractive forces between different molecules then it is called adhesive force. When the cohesive force between the water molecules is greater than the adhesive force of water molecules with the solid molecules, then it cannot stick on the surface. You can see a drop of water on such a surface (hydrophobic) forms a round ball and go in crazy directions. So there will be no wetting. Now in some hydrophilic surfaces, the adhesive force between the liquid and solid molecules dominate and the liquid molecules stick on to the surface. This makes the surface wet.
So the degree of wetting is determined by a force balance between adhesive and cohesive forces.
A liquid has it's own inter molecular force of attraction that maintains it's continuity. Such forces existing between same type of molecules is called cohesive force. Now if there is some inter molecular attractive forces between different molecules then it is called adhesive force. When the cohesive force between the water molecules is greater than the adhesive force of water molecules with the solid molecules, then it cannot stick on the surface. You can see a drop of water on such a surface (hydrophobic) forms a round ball and go in crazy directions. So there will be no wetting. Now in some hydrophilic surfaces, the adhesive force between the liquid and solid molecules dominate and the liquid molecules stick on to the surface. This makes the surface wet.
So the degree of wetting is determined by a force balance between adhesive and cohesive forces.
definitelyslayer:
can you marm it brainliest please
Answered by
8
If mercury is taken in a glass vessel, the free surface of mercury near the walls is convex upwards. When the liquid is in contact with solid, the angle between the solid surface and the tangent to the free surface of liquid at the point of contact, measured from inside the liquid is called the angle of contact.
If the contact angle between a liquid and a solid is <90°, the liquid will wet the surface and spread over it. If the contact angleis ≥90°, the liquid will stay on the surface as a bead. Therefore, the contact angle between a liquid and a solid is dependent on the nature of the liquid as well as the surface characteristics of the solid.
If the contact angle between a liquid and a solid is <90°, the liquid will wet the surface and spread over it. If the contact angleis ≥90°, the liquid will stay on the surface as a bead. Therefore, the contact angle between a liquid and a solid is dependent on the nature of the liquid as well as the surface characteristics of the solid.
Similar questions